We all know that movie ticket prices aren't what they used to be. The cost of consumer goods and services rise each year. So, taking inflation into account is the only way to meaningfully compare the box office collection of movies over time.
Ideally we should use India inflation rate for adjusting box office collection in India and inflation rate from respective countries for overseas collection. For simplicity, our calculations assume US inflation rate as the basis for adjusting the box office collection of all overseas countries.
We also take into account the currency rate change over a period of time to accurately calculate the present box office collection values of historical movies.